Composition for high performance glass fibers and fibers formed therewith

ABSTRACT

A composition for the manufacture of high strength glass fibers suitable for manufacture in a refractory lined glass melter is disclosed. The glass composition of the present invention includes 64-75 weight % SiO 2 , 16-24 weight % Al 2 O 3 , 8-11 weight % MgO and 0.25 to 3.0 weight % R 2 O where R 2 O is the sum of Li 2 O and Na 2 O. A composition of the present invention includes 64-75 weight % SiO 2 , 16-24 weight % Al 2 O 3 , 8-11 weight % MgO and 0.25 to 3.0 weight % Li 2 O. Another composition includes 68-69 weight percent SiO 2 , 20-22 weight percent Al 2 O 3 , 9-10 weight percent MgO and 1-3 weight percent Li 2 O. By using oxide based refractory lined furnaces the cost of production of glass fibers is substantially reduced in comparison with the cost of fibers using a platinum lined melting furnace. Fibers formed by the present invention are also disclosed. The fibers have a fiberizing temperature of less than 2650° F., a ΔT of at least 80° F. Further, the glass fibers have a strength in excess of 680 KPSI, in some instances a strength in excess of about 700 KPSI, and in others a strength in excess of about 730 KPSI. The glass fibers will desirably have a modulus greater than 12.0 MPSI, in some instances greater than about 12.18 MPSI, and in certain instances greater than about 12.7 MPSI.

TECHNICAL FIELD AND INDUSTRIAL APPLICABILITY OF THE INVENTION

The present invention is generally directed to a composition for use inmanufacturing continuous high strength glass fibers and fibers formedfrom the composition.

BACKGROUND OF THE INVENTION

A common glass composition for making continuous high-strength glassfiber strands is “S-Glass.” The term S-Glass defines a family of glassescomposed primarily of the oxides of magnesium, aluminum, and siliconwith a chemical composition that produces glass fibers having a highermechanical strength than E-Glass fibers. The chemical composition of theS-glass family produces high strength glass fiber and enables theseglasses to be used in high strength applications such as ballisticarmor. ASTM International defines S-Glass as family of glasses composedprimarily of the oxides of magnesium, aluminum, and silicon with acertified chemical composition which conforms to an applicable materialspecification and which produces high mechanical strength (D578-05). TheDeutsches Institut für Normung (DIN) defines S-Glass as analuminosilicate glass without added CaO and having a partial mass of MgOwhere MgO is about 10% by weight (An alumino-silicate glass is definedas a glass which consists largely of aluminum trioxide and silicondioxide and other oxides) (DIN 1259-1).

R-Glass is another family of high strength, high modulus glasses that istypically formed into fibers for use in aerospace compositeapplications. The R-Glass family is primarily composed of silicon oxide,aluminum oxide, magnesium oxide, and calcium oxide with a chemicalcomposition that produces glass fibers with a higher mechanical strengththan S-Glass fibers. R-Glass generally contains less silica and greatercalcium oxide (CaO) than S-Glass which requires higher melting andprocessing temperatures during fiber forming.

Tables IA-IE set forth the compositions for a number of conventionalhigh strength glass compositions.

TABLE I-A RUSSIAN Chinese CONTINUOUS NITTOBO NITTOBO High ROVING “T” “T”Strength MAGNESIUM Glass Glass Fabric Constituent glass ALUMINOSILICATEFabric “B” (Yarn) “C” SiO₂ 55.08 55.81 64.58 64.64 CaO 0.33 0.38 0.440.40 Al₂O₃ 25.22 23.78 24.44 24.57 B₂O₃ 1.85 0.03 0.03 MgO 15.96 15.089.95 9.92 Na₂O 0.12 0.063 0.08 0.09 Fluorine 0.03 0.034 0.037 TiO₂ 0.0232.33 0.019 0.018 Fe₂O₃ 1.1 0.388 0.187 0.180 K₂O 0.039 0.56 0.007 0.010ZrO₂ 0.007 0.15 Cr₂O₃ 0.011 0.003 0.003 Li₂O 1.63 CeO₂

TABLE I-B Nitto Nitto Vetrotex Saint Boseki Boseki Nitto Boseki TEGobain SR Glass Polotsk A&P NT6030 Glass RST- Stratifils SR CGSTEKLOVOLOKNO Constituent Yarn Yarn 220PA-535CS 250 P109 High StrengthGlass SiO₂ 65.51 64.60 64.20 63.90 58.64 CaO 0.44 0.58 0.63 0.26 0.61Al₂O₃ 24.06 24.60 25.10 24.40 25.41 B₂O₃ 0.04 MgO 9.73 9.90 9.90 10.0014.18 Na₂O 0.04 0.06 0.020 0.039 0.05 Fluorine 0.07 0.02 TiO₂ 0.0160.000 0.000 0.210 0.624 Fe₂O₃ 0.067 0.079 0.083 0.520 0.253 K₂O 0.0200.020 0.020 0.540 0.35 ZrO₂ 0.079 Cr₂O₃ 0.0010 0.001 0.023 Li₂O CeO₂

TABLE I-C Chinese Advanced High Glass Chinese High Strength YarnsStrength Yarn Glass Zentron S-2 SOLAIS Glass Constituent (8 micron)Roving Glass Roving Sample SiO₂ 55.22 55.49 64.74 64.81 CaO 0.73 0.290.14 0.55 Al₂O₃ 24.42 24.88 24.70 24.51 B₂O₃ 3.46 3.52 0.02 MgO 12.4612.28 10.24 9.35 Na₂O 0.104 0.06 0.17 0.16 Fluorine 0.07 0.02 TiO₂ 0.320.36 0.015 0.04 Fe₂O₃ 0.980 0.930 0.045 0.238 K₂O 0.240 0.150 0.005 0.03ZrO₂ Cr₂O₃ 0.0050 0.007 Li₂O 0.59 0.63 CeO₂ 1.23 1.25

TABLE I-D Advanced IVG IVG IVG Vertex Glass Vertex Vertex Outside YarnsCulimeta B96 Glass #1 Glass Constituent S Glass Roving 675 Yarn RovingRoving SiO₂ 64.61 59.37 58.34 58.58 58.12 CaO 0.17 0.27 0.31 0.30 0.31Al₂O₃ 24.84 25.49 23.81 24.26 24.09 B₂O₃ 0.04 0.05 MgO 10.11 13.47 14.9915.02 15.36 Na₂O 0.118 0.024 0.05 0.02 0.03 Fluorine 0.03 0.04 0.04 0.04TiO₂ 0.011 0.530 1.380 0.67 0.91 Fe₂O₃ 0.042 0.374 0.333 0.336 0.303 K₂O0.48 0.42 0.28 0.29 ZrO₂ 0.152 0.129 0.165 0.157 Cr₂O₃ 0.0050 0.01200.0100 0.0120 0.0120 Li₂O CeO₂

TABLE I-E IVG Vertex RH CG250 P109 Outside #2 Glass Fiber ConstituentGlass Roving Strand SiO₂ 58.69 58.54 CaO 0.29 9.35 Al₂O₃ 24.3 25.39 B₂O₃MgO 15.06 6.15 Na₂O 0.03 0.10 Fluorine 0.04 0.16 TiO₂ 0.64 0.008 Fe₂O₃0.331 0.069 K₂O 0.36 0.14 ZrO₂ 0.187 0.006 Cr₂O₃ 0.0130 Li₂O CeO₂

Typical R-Glass and S-Glass are generally produced by melting theconstituents of the compositions in a platinum lined melting container.The costs of forming R-Glass and S-Glass fibers are dramatically higherthan E-Glass fibers due to the cost of producing the fibers in suchmelters. Thus, there is a need in the art for methods of forming glasscompositions useful in the formation of high performance glass fibers ina more cost-effective process.

SUMMARY OF THE INVENTION

The present invention is a glass composition for the formation ofcontinuous glass fibers suitable for use in high strength applications.The composition may be inexpensively formed into glass fibers usinglow-cost, direct melting in refractory-lined furnaces due to therelatively low fiberizing temperature of the composition. Once formedinto fibers, the glass composition provides the strength characteristicsof S-Glass. One composition of the present invention includes 64-75weight % SiO₂, 16-24 weight % Al₂O₃, 8-11 weight % MgO and 0.25 to 3.0weight % R₂O where R₂O is the sum of Li₂O and Na₂O. The composition ofthe present invention includes 64-75 weight % SiO₂, 16-24 weight %Al₂O₃, 8-11 weight % MgO and 0.25 to 3.0 weight % Li₂O. In certainembodiments, the glass composition is composed of 64-70 weight % SiO₂,17-22 weight % Al₂O₃, 9-11 weight % MgO and 1.75-3.0 weight % R₂O whereR₂O is the sum of Li₂O and Na₂O. In another embodiment, the glasscomposition is composed of 64-70n weight % SiO₂, 17-22 weight % Al₂O₃,9-11 weight % MgO and 1.75-3.0 weight % LiO₂. In certain embodiments,the composition does not contain more than about 5.0 weight % of oxidesor compounds selected from the group consisting of CaO, P₂O₅, ZnO, ZrO₂,SrO, BaO, SO₃, F₂, B₂O₃, TiO₂ and Fe₂O₃.

The desired properties of the high performance composite fibersmanufactured by the present invention include a fiberizing temperatureof less than about 2650° F., less than about 2625° F., less than about2600° F., or even less than about 2575° F. and a liquidus temperaturethat is below the fiberizing temperature, in some instances by at least80° F., in others by at least about 120° F., and in certain otherinstances by at least about 150° F. The present invention also includesfibers formed from such a composition.

DETAILED DESCRIPTION AND PREFERRED EMBODIMENTS OF THE INVENTION

The fiberizing properties of the glass batch composition of the presentinvention include the fiberizing temperature, the liquidus, and delta-T(ΔT). The fiberizing temperature is defined as the temperature thatcorresponds to a viscosity of 1000 Poise. As discussed in more detailbelow, a lowered fiberizing temperature reduces the production cost ofthe fibers, allows for a longer bushing life, increases throughputpermits the glass to be melted in a refractory-lined melter, and reducesenergy consumption. For example, at a lower fiberizing temperature, abushing operates at a cooler temperature and does not “sag” as quickly.Sag is a phenomenon that occurs in bushings that are held at an elevatedtemperature for extended periods of time. By lowering the fiberizingtemperature, the sag rate of the bushing may be reduced and the bushinglife can be increased. In addition, a lower fiberizing temperatureallows for a higher throughput since more glass can be melted in a givenperiod at a given energy input. As a result, production cost is reduced.In addition, a lower fiberizing temperature will also permit glassformed with the inventive composition to be melted in a refractory-linedmelter since both its melting and fiberizing temperatures are below theupper use temperatures of many commercially available refractories.

The liquidus of a glass is defined as the highest temperature at whichequilibrium exists between liquid glass and its primary crystallinephase. At all temperatures above the liquidus, the glass is free fromcrystals in its primary phase. At temperatures below the liquidus,crystals may form. Crystals in the melt will cause blockages in thebushing and weakness in the fibers.

Another fiberizing property is delta-T (ΔT), which is defined as thedifference between the fiberizing temperature and the liquidus. A largerΔT offers a greater degree of flexibility during the formation of theglass fibers and helps to inhibit devitrification of the glass (that is,the formation of crystals within the melt) during melting andfiberizing. Increasing the ΔT also reduces the production cost of theglass fibers by allowing for a greater bushing life and by providing awider process window for forming fibers.

The glasses of the present invention are suitable for melting intraditional commercially available refractory-lined glass melters thatare widely used in the manufacture of glass reinforcement fibers, inwhat is commonly called a direct-melt process. This is contrasted toprior art formulations, which were melted in a platinum lined meltingcontainer, since those prior art formulations typically do not haveproperties which are compatible with direct-melt processes. With thepresent invention, starting batch components typically include SiO₂(ground silica sand), and Al₂O₃ (calcined alumina) or pyrophyllite, aswell as chain modifiers from source materials such as talc, magnesite ordolomite. The carbon included in materials such as magnesite is offgassed as oxides of carbon such as CO₂.

In certain embodiments, a fiber formed in accordance with the presentinvention will include 64-75 weight % SiO₂, 16-24 weight % Al₂O₃, 8-11weight % MgO and 0.25 to 3.0 weight % R₂O where R₂O is the sum of Li₂Oand Na₂O. In other embodiments, the composition will include 0.25 to 3.0weight % Li₂O rather than a combination of Li₂O and Na₂O. In yet otherembodiments, the glass composition is composed of 64-70 weight % SiO₂,17-22 weight % Al₂O₃, 9-11 weight % MgO and 1.75 to 3.0 weight % R₂Owhere R₂O is the sum of Li₂O and Na₂O. In certain other embodiments, thecomposition will include 1.75 to 3.0 weight % LiO₂. A fiber formed inaccordance with the present invention will typically include smallamounts of CaO, P₂O₅, ZnO, ZrO₂, SrO, BaO, SO₃, F₂, B₂O₃, TiO₂ andFe₂O₃., in certain embodiments in a total amount of less than 5 weightpercent, and in other embodiments less than about 4 weight percent. Inaddition, a fiber formed in accordance with the method and compositionof the present invention will having a fiberizing temperature of lessthan 2650° F., and in certain embodiments less than about 2625° F., inother embodiments less than about 2600° F. and in certain embodimentsless than about 2575° F. and a liquidus temperature that is below thefiberizing temperature in certain embodiments by at least 80° F., and inother embodiments by at least about 120° F., and in yet otherembodiments by at least about 150° F. Further, the glass of the presentinvention in certain embodiments will have a pristine fiber strength inexcess of 680 KPSI, and in certain other embodiments a strength inexcess of about 700 KPSI, and in yet other embodiments a strength inexcess of about 730 KPSI. Further, the glass fibers will desirably havea modulus greater than 12.0 MPSI, and in certain embodiments greaterthan about 12.18 MPSI, and in some embodiments greater than about 12.6MPSI.

The glass batch of the present invention is melted, in some instancesusing a glass melting furnace made from appropriate refractory materialssuch as alumina, chromic oxide, silica, alumina-silica, zircon,zirconia-alumina-silica, or similar oxide-based refractory materials.Often, such glass melting furnaces include one more bubblers and/orelectrical boost electrodes (One suitable glass melting furnace isdisclosed in U.S. Application Number 20070105701 entitled “Method ofManufacturing High Performance Glass Fibers in a Refractory Lined Melterand Fiber Formed Thereby” herein incorporated by reference). Thebubblers and/or electrical boost electrodes increase the temperature ofthe bulk glass and increase the molten glass circulation under the batchcover.

The melted glass is delivered to a bushing assembly from a forehearth.The bushing includes a tip plate with a plurality of nozzles, eachnozzle discharges a stream of molten glass, which are mechanically drawnto form continuous filaments. Typically, the filaments are coated with aprotective sizing, gathered into a single continuous strand and woundonto a rotating collet of a winder device to form a package. Thefilaments may also be processed into other forms including, withoutlimitation, wet used chopped strand fibers, dry use chopped strandfibers, continuous filament mats, chopped strand mats, wet formed matsor air laid mats.

Having generally described this invention, a further understanding canbe obtained by reference to certain specific examples illustrated belowwhich are provided for purposes of illustration only and are notintended to be all inclusive or limiting unless otherwise specified.

EXAMPLES

The glasses in the examples listed in Tables IIA-IID were melted inplatinum crucibles or in a continuous platinum-lined melter fordetermining the mechanical and physical properties of the glass andfibers produced therefrom. The units of measurement for the physicalproperties are: Viscosity (° F.), Liquidus temperature (° F.) and ΔT (°F.). In some examples the glasses were fiberized and Strength (KPsi),Density (g/cc), Modulus (MPsi) were measured.

The fiberizing temperature was measured using a rotating spindleviscometer. The fiberizing viscosity is defined as 1000 Poise. Theliquidus was measured by placing a platinum container filled with glassin a thermal gradient furnace for 16 hours. The greatest temperature atwhich crystals were present was considered the liquidus temperature. Themodulus was measured using the sonic technique on a single fiber ofglass. The tensile strength was measured on a pristine single fiber.

TABLE IIA Glass Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 SiO₂ 67.2 69 67 7070 65 Al₂O₃ 20 22 22 17 17 21 MgO 9.8 9 11 11 10 11 Li₂O 3 0 0 2 3 3Measured 2531 2761 2648 2557 2558 2461 Viscosity (° F.) 1^(st) Measured2313 2619 2597 2332 2302 2296 Liquidus (° F.) 2^(nd) Measured 2302 26202614 2346 2308 2318 Liquidus (° F.) ΔT (° F.) 218 142 51 225 256 165Measured 2.459 2.452 2.481 2.450 2.441 2.482 Density (g/cc)

TABLE II-B Glass Ex. 7 Ex. 8 Ex. 9 Ex. 10 Ex. 11 Ex. 12 SiO₂ 70 69 70 6566 65 Al₂O₃ 18 17 21 22 22 22 MgO 9 11 9 11 9 10 Li₂O 3 3 0 2 3 3Measured 2544 2496 2752 2525 2523 2486 Viscosity (° F.) 1^(st) Measured2311 2234 2597 2468 2391 2361 Liquidus (° F.) 2^(nd) Measured 2324 23432603 2462 2394 2382 Liquidus (° F.) ΔT (° F.) 233 262 155 57 132 125Measured 2.434 2.455 2.443 2.486 2.460 2.474 Density (g/cc)

TABLE II-C Glass Ex. 13 Ex. 14 Ex. 15 Ex. 16 Ex. 17 Ex. 18 SiO₂ 70 67.3267.57 68.27 68.02 67.76 Al₂O₃ 19 20.49 20.49 20.10 20.10 20.10 MgO 1110.00 10.00 9.69 9.69 9.69 Li₂O 0 2.00 1.75 1.75 2.00 2.25 MeasuredViscosity 2679 2563 2584 2598 2578 2547 (° F.) 1^(st) Measured Liquidus2596 2456 2486 2446 2431 2399 (° F.) 2^(nd) Measured 2582 2447 2469 24692437 2406 Liquidus (° F.) ΔT (° F.) 83 111.5 106.5 140.5 144 144.5Measured 2.453 2.461 2.452 Density (g/cc)

The composition of the present invention may also include chainmodifiers such as Na₂O, CaO and B₂O₃. Such compositions are shown inTable II-D (below).

TABLE II-D Glass Ex. 19 Ex. 21 Ex. 22 Ex. 22 Ex. 23 Ex. 24 SiO₂ 75 66 6565 66 74 Al₂O₃ 15 20 20 24 19 15 MgO 8 9 8 8 9 8 Li₂O 1 1 2 0 0 0 Na₂O 12 1 1 2 3 CaO 2 4 B₂O₃ 2 4 Measured 2765 2607 2469 2669 2809 Viscosity(° F.) 1^(st) Measured 2422 2729 2614 2630 2680 Liquidus (° F.) ΔT (°F.) 343 −122 55 129

The fibers of the present invention have superior modulus and strengthcharacteristics. The fibers of Example 1 have a Measured Modulus of12.71 MPsi and a Measured Strength of 688 KPsi. The fibers of Example 3have a Measured Modulus of 12.96 MPsi and a Measured Strength of 737KPsi. The fibers of Example 17 have a Measured Modulus of 12.75 MPsi anda Measured Strength of 734 KPsi.

As is understood in the art, the above exemplary inventive compositionsdo not always total 100% of the listed components due to statisticalconventions (such as, rounding and averaging) and the fact that somecompositions may include impurities that are not listed. Of course, theactual amounts of all components, including any impurities, in acomposition always total 100%. Furthermore, it should be understood thatwhere small quantities of components are specified in the compositions,for example, quantities on the order of about 0.05 weight percent orless, those components may be present in the form of trace impuritiespresent in the raw materials, rather than intentionally added.

Additionally, components may be added to the batch composition, forexample, to facilitate processing, that are later eliminated, therebyforming a glass composition that is essentially free of such components.Thus, for instance, minute quantities of components such as fluorine andsulfate may be present as trace impurities in the raw materialsproviding the silica, calcia, alumina, and magnesia components incommercial practice of the invention or they may be processing aids thatare essentially removed during manufacture.

As apparent from the above examples, glass fiber compositions of theinvention have advantageous properties, such as low fiberizingtemperatures and wide differences between the liquidus temperatures andthe fiberizing temperatures (high ΔT values). Other advantages andobvious modifications of the invention will be apparent to the artisanfrom the above description and further through practice of theinvention). The high-performance glass of the present invention meltsand refines at relatively low temperatures, has a workable viscosityover a wide range of relatively low temperatures, and a low liquidustemperature range.

The invention of this application has been described above bothgenerically and with regard to specific embodiments. Although theinvention has been set forth in what is believed to be the preferredembodiments, a wide variety of alternatives known to those of skill inthe art can be selected within the generic disclosure. Other advantagesand obvious modifications of the invention will be apparent to theartisan from the above description and further through practice of theinvention. The invention is not otherwise limited, except for therecitation of the claims set forth below.

1. A composition for high strength glass fibers, formable from a directmelt process, comprising: 64-75 weight percent SiO₂; 16-24 weightpercent Al₂O₃; 8-12 weight percent MgO; and 0.25-3 weight percent R₂O,where R₂O equals the sum of Li₂O and Na₂O; the composition having aliquidus of less than about 2550° F.
 2. The composition for highstrength glass fibers 1, wherein the glass batch comprises less than 5weight percent total of compounds selected from the group consisting ofCaO, P₂O₅, ZnO, ZrO₂, SrO, BaO, SO₃, F₂, B₂O₃, TiO₂ and Fe₂O₃.
 3. Thecomposition for high strength glass fibers 1, wherein glass producedfrom said batch has a fiberizing temperature of less than about 2650°F., and a ΔT of at least 80° F.
 4. A composition for high strength glassfibers 3 wherein glass produced from said batch has a ΔT of at least120° F.
 5. A composition for high strength glass fibers 1, wherein glassproduced from said batch has a fiberizing temperature of less than 2600°F., and a ΔT of at least 140° F.
 6. The composition for high strengthglass fibers 1, wherein the glass batch further comprises 0 to 3 weightpercent alkali metal oxides.
 7. A composition for high strength glassfibers 1, wherein the composition comprises: 68-69 weight percent SiO₂;20-22 weight percent Al₂O₃; 9-10 weight percent MgO; and 1-3 weightpercent Li₂O.
 8. A composition for high strength glass fibers, formablefrom a direct melt process, comprising: 65-69 weight percent SiO₂; 20-22weight percent Al₂O₃; 9-11 weight percent MgO; and 0.25-3 weight Li₂O.the composition having a liquidus of less than about 2650° F.
 9. Thecomposition for high strength glass fibers of claim 8, wherein thecomposition comprises: about 68 weight percent SiO₂; about 20 weightpercent Al₂O₃; about 10 weight percent MgO; and about 2 weight Li₂O. 10.The composition for high strength glass fibers of claim 8, wherein thecomposition consists essentially of: about 68 weight percent SiO₂; about20 weight percent Al₂O₃; about 9.7 weight percent MgO; and about 2weight Li₂O.
 11. The composition for high strength glass fibers of claim10, wherein the modulus is at least 12.7 MPsi.
 12. The composition forhigh strength glass fibers of claim 10, wherein the ΔT is at least 140°F.
 13. A composition for high strength glass fibers 8, wherein glassproduced from said batch has a fiberizing temperature of less than 2600°F., and a ΔT of at least 144° F.
 14. A high strength glass fiber formedby melting a glass batch in a refractory lined glass melter, comprising:64-75 weight percent SiO₂; 16-24 weight percent Al₂O₃; 8-12 weightpercent MgO; and 0.25-3 weight percent R₂O, where R₂O equals the sum ofLi₂O and Na₂O.
 15. The high strength glass fiber of claim 14, whereinthe fiber has a modulus greater than 12.0 MPSI.
 16. The high strengthglass fiber of claim 14, wherein the fiber has a modulus greater than12.7 MPSI.
 17. The high strength glass fiber of claim 14, wherein thefiber has a strength greater than 688 KPSI.
 18. The high strength glassfiber of claim 14, wherein the fiber has a strength greater than 700KPSI.
 19. The high strength glass fiber of claim 14, wherein the atleast 75% of the R₂O is Li₂O.
 20. The high strength glass fiber of claim14, comprising: 68-69 weight percent SiO₂; 20-22 weight percent Al₂O₃;9-10 weight percent MgO; and 1-3 weight percent Li₂O.